Rhonin died saving Jaina during the attack on Theramore. The only reason you still see him in game is because Dalaran that you see in Northrend is actually in the past. Blizzards timelines are usually muddled.

I never told Trassk that he DIDN'T actually die in the lore, I said that in-game blizzard has allowed him to survive regarding the amount of quests leading up to rhonin.
In-game he IS alive, In the lore is death.

Shit like this is why cremation is the only sensible method of disposal for... basically any corpse anywhere in fantasy. Seriously, why is anyone still burying their dead in a world where necromancy exists?